Multi-carrier transmitter apparatus, multi-carrier receiver apparatus and multi-carrier communication method

ABSTRACT

Multicarrier transmission apparatus  100  receives channel quality information of subcarriers from multicarrier reception apparatus  200  and interleave pattern setting section  108  sets an interleave pattern according to channel quality of subcarriers. Interleaver  106  interleaves I components and/or Q components of symbols using the set interleave pattern. As a result, it is possible to optimize diversity gains in modulation diversity modulation/demodulation according to channel quality.

TECHNICAL FIELD

The present invention relates to a multicarrier transmission apparatus,multicarrier reception apparatus and multicarrier communication methodusing a modulation diversity technology in particular.

BACKGROUND ART

A multicarrier communication apparatus using an OFDM (OrthogonalFrequency Division Multiplexing) scheme is becoming a focus of attentionas an apparatus capable of realizing high-speed radio transmission inrecent years because of its resistance to multipath or fading andability to carry out high quality communication. Furthermore, there is aproposal to apply a technology called a “modulation diversitymodulation/demodulation” to a multicarrier communication to furtherimprove communication quality.

Modulation diversity modulation/demodulation in a conventionalmulticarrier communication apparatus is described in a document “3GPPTSG RAN WG1 #31 R1-030156 “Modulation diversity for OFDM.””

This modulation diversity modulation/demodulation will be explainedbriefly using FIG. 1. FIG. 1 shows a case where QPSK (Quadrature PhaseShift Keying) is performed as an example of modulation scheme. Atransmitter rotates the phases of symbols mapped to an IQ plane by apredetermined angle as shown in (a) of FIG. 1. Next, the transmitterinterleaves an Ich component and Qch component using separate uniform orrandom interleavers for the Ich and Qch. This causes the signal after aninverse Fourier transform (IFFT) to be assigned to subcarriers havingIch components and Qch components of symbols which are different fromthose before interleaving as shown in (b) of FIG. 1. In the case of (b)of FIG. 1, the Ich components are assigned to subcarrier B and the Qchcomponents are assigned to subcarrier A.

A receiver extracts the Ich components and Qch components superimposedon the subcarriers by carrying out a fast Fourier transform (FFT) first.Next, the Ich and Qch are restored to their original arrays by carryingout deinterleaving. Then, the receiver obtains received data by carryingout demapping processing based on a constellation of the Ich and Qchrestored to their original arrays.

Here, suppose subcarrier A has a good channel condition and subcarrier Bhas a bad channel condition, which results in a constellation which isone-sided toward the Qch direction as shown in (c) of FIG. 1. Thisallows signal points in the constellation to be kept relatively far fromone another making it possible to reconstruct bits in a packet averagelycorrectly during demapping. Thus, modulation diversitymodulation/demodulation can achieve an effect similar to that ofdistributing SNR (Signal-to-Noise Ratio) in the subcarrier directionsand carrying out corrections even when fading variations occur in therespective subcarriers due to multipath fading.

As a result, modulated symbols are affected by a variation as if theywere transmitted through an AWGN (Additive White Gaussian Noise)communication path, and therefore it is possible to obtain a diversitygain.

FIG. 2 shows the configuration of multicarrier transmission apparatus 10that carries out modulation diversity transmission processing andmulticarrier reception apparatus 20 that receives and demodulates thesignal.

Multicarrier transmission apparatus 10 includes modulation diversitymodulation section 11 and inputs transmission data to mapping section 12of modulation diversity modulation section 11. Mapping section 12 mapstransmission data to the IQ plane according to a modulation scheme suchas BPSK (Binariphase Phase Shift Keying), QPSK (Quadrature Phase ShiftKeying), 16QAM (Quadrature Amplitude Modulation).

The phases of the mapped symbols are rotated by a predetermined angle atphase rotation section 13 as shown in (a) of FIG. 1. The phase-rotatedsymbols are separated into Ich components and Qch components by IQseparation section 14, one of the Ich component and Qch component issent to interleaver 16 and the other is sent to IQ combination section15. The Ich component or Qch component interleaved in an interleavepattern predetermined by interleaver 16 are sent to IQ combinationsection 15.

IQ combination section 15 restores the constellation by combining theIch components and Qch components. Modulation diversity modulationsymbols are obtained in this way. The modulation diversity modulationsymbols are superimposed on predetermined subcarriers by serial/parallelconversion section (S/P) 17 and inverse fast Fourier transform section(IFFT). That is, serial/parallel conversion section (S/P) 17 and inversefast Fourier transform section (IFFT) 18 assign the modulation diversitymodulation symbols to any one of a plurality of subcarriers which areorthogonal to each other and modulate the subcarriers sequentially usingthe modulation diversity modulation symbols.

Thus, interleaver 16 of multicarrier transmission apparatus 10 carriesout interleave processing on any one of the I component and Q component,and therefore one of the I component and Q component is fixed to onesubcarrier but the other component is placed on a subcarrier whichvaries depending on the interleave pattern. The signal after IFFTprocessing is subjected to radio transmission processing such asanalog/digital conversion processing and up-conversion by radiotransmission section 19 and transmitted via an antenna.

Multicarrier reception apparatus 20 that receives and demodulates asignal transmitted from multicarrier transmission apparatus 10 includesmodulation diversity demodulation section 21. Multicarrier receptionapparatus 20 applies radio reception processing such as down-conversionand analog/digital conversion processing on a radio signal received viaan antenna using radio reception section 22 and then sends the signal tofast Fourier transform section (FFT) 23. FFT section 23 extracts themodulation diversity modulation symbols superimposed on the respectivesubcarriers. These modulation diversity modulation symbols superimposedon the subcarriers are sent to IQ separation section 25 of modulationdiversity demodulation section 21 via parallel/serial conversion section(P/S) 24.

IQ separation section 25 separates the symbols into I components and Qcomponents. Then, IQ separation section 25 sends components which havenot been interleaved on the transmitting side out of the separatedcomponents directly to IQ combination section 26 and sends thecomponents which have been interleaved on the transmitting side todeinterleaver 27. Deinterleaver 27 restores the interleaved componentsto the original array by carrying out the reverse processing ofinterleaver 16 and sends them to IQ combination section 26. As a result,the IQ combination section obtains symbols consisting of pairs oforiginal I components and Q components as the combination result.

Phase rotation section 28 rotates the phase of the combined symbol inthe opposite direction by the same angle as that of phase rotationsection 13 on the transmitting side. Demapping section 29 outputsreceived data in accordance with the symbol constellation after thephase rotation.

As described above, if modulation diversity modulation/demodulation isapplied to an OFDM scheme, transmission can be performed with the Icomponent and Q component of a modulated symbol arranged on differentsubcarriers, and therefore even when the channel condition of a certainsubcarrier is bad due to frequency selective fading during transmission,it is possible to obtain correct received data if the channel conditionof the subcarrier on which one of the I component and Q component isplaced is good. As a result, it is possible to improve an errorcorrection rate characteristic of the received data.

However, since a conventional modulation diversitymodulation/demodulation uses an interleaver in a predeterminedinterleave pattern, the reception sensitivities of the Ich component andQch component of transmission symbols vary without any correlation dueto effects of frequency selective fading. For this reason, channelconditions of both the subcarrier to which Ich is assigned and thesubcarrier to which Qch is assigned may be improved. On the contrary,channel conditions of both the subcarrier to which Ich is assigned andthe subcarrier to which Qch is assigned may deteriorate. This may resultin deterioration of the error correction rate characteristic withoutobtaining any effective diversity gain.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a multicarriertransmission apparatus, multicarrier reception apparatus andmulticarrier communication method capable of further improving an errorcorrection rate characteristic when a modulation diversity technology isused.

This object can be attained when modulation diversitymodulation/demodulation is performed by adaptively changing aninterleave pattern and deinterleave pattern of modulation diversitymodulation/demodulation according to channel quality of subcarriers.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates principles of modulation diversitymodulation/demodulation;

FIG. 2 is a block diagram showing the configuration of a multicarriertransmission apparatus and multicarrier reception apparatus to realizeconventional modulation diversity modulation/demodulation;

FIG. 3 is a block diagram showing the configuration of a multicarriertransmission apparatus and multicarrier reception apparatus according toEmbodiment 1 of the present invention;

FIG. 4 is a timing chart showing exchanges of control information anddata between multicarrier transmission/reception apparatuses accordingto the embodiment;

FIG. 5A illustrates a propagation path variation (scaling factor) ofsubcarriers;

FIG. 5B is a diagram provided to illustrate an explanation of theoperation of the multicarrier transmission apparatus according to theembodiment when subcarriers change as shown in FIG. 5A;

FIG. 6 illustrates a signal point position after BPSK modulation whenthe phase of the signal is rotated by 45°;

FIG. 7 illustrates a signal point position before demapping ofmodulation diversity modulation symbols obtained by Embodiment 1;

FIG. 8 is a characteristic curve diagram showing a comparison of anaverage error rate of conventional modulation diversitymodulation/demodulation and that of modulation diversitymodulation/demodulation according to this embodiment;

FIG. 9 is a block diagram showing the configurations of a multicarriertransmission apparatus and multicarrier reception apparatus according toEmbodiment 2;

FIG. 10 is a block diagram showing the configuration of an interleavepattern setting section according to Embodiment 2;

FIG. 11 is a block diagram showing the configurations of a multicarriertransmission apparatus and multicarrier reception apparatus according toEmbodiment 3;

FIG. 12 is a block diagram showing the configuration of an interleavepattern setting section according to Embodiment 3;

FIG. 13A illustrates SNR values of subcarriers;

FIG. 13B shows an example of feedback information according toEmbodiment 4;

FIG. 14A illustrates SNR values of subcarriers;

FIG. 14B shows an example of feedback information according toEmbodiment 4;

FIG. 15A illustrates SNR values of subcarriers;

FIG. 15B shows an example of feedback information according toEmbodiment 4;

FIG. 16A illustrates SNR values of subcarriers;

FIG. 16B illustrates subcarrier numbers in descending order of a channelcondition as feedback information 1;

FIG. 16C illustrates subcarrier numbers in ascending order of a channelcondition as feedback information 2;

FIG. 16D illustrates subcarrier numbers which are not sent as feedbackinformation;

FIG. 17 is a diagram provided to illustrate a method of interleaving onsubcarriers of high, medium and low channel quality according toEmbodiment 4;

FIG. 18 is a diagram provided to illustrate a method of settingthresholds when classifying channel quality;

FIG. 19 is a diagram provided to illustrate a relationship between aDoppler frequency, frequency of transmitting feedback information andswitching between interleave methods;

FIG. 20 is a block diagram showing the configurations of a multicarriertransmission apparatus and multicarrier reception apparatus according toEmbodiment 5;

FIG. 21 is a diagram provided to illustrate the operation of themulticarrier transmission apparatus according to Embodiment 5;

FIG. 22 illustrates reception constellations obtained by themulticarrier reception apparatus according to Embodiment 5; and

FIG. 23 illustrates the operation according to Embodiment 5 when anotherconfiguration is applied.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference now to the attached drawings, embodiments of the presentinvention will be explained in detail below.

Embodiment 1

FIG. 3 shows the configuration of multicarrier transmission apparatus100 and multicarrier reception apparatus 200 according to a multicarriercommunication apparatus of the present invention. Multicarriertransmission apparatus 100 is provided on a first radio station andmulticarrier reception apparatus 200 is provided on a second radiostation that carries out radio communication with the first radiostation.

In practice, the first radio station provided with multicarriertransmission apparatus 100 includes a reception section and the secondradio station provided with multicarrier reception apparatus 200includes a transmission section, but the reception section andtransmission section of this embodiment are omitted in the explanationsfor simplicity.

Multicarrier transmission apparatus 100 includes modulation diversitymodulation section 101 and inputs transmission data to mapping section102 of modulation diversity modulation section 101. Mapping section 102maps the transmission data to an IQ plane according to a modulationscheme such as BPSK (Binariphase Phase Shift Keying), QPSK (QuadraturePhase Shift Keying), 16QAM (Quadrature Amplitude Modulation).

The phases of symbols after mapping are rotated by a predetermined angleat phase rotation section 103 as shown in (a) of FIG. 1. Here, mappingsection 102 and phase rotation section 103 function as a symbolformation section that forms symbols. The symbols whose phases have beenrotated are separated into Ich components and Qch components by IQseparation section 104 and one of the Ich component and Qch component issent to interleaver 106 and the other is sent to IQ combination section105. In this embodiment, Ich components are directly sent to IQcombination section 105 and Qch components are sent to interleaver 106.

Interleaver 106 carries out interleave processing using an interleavepattern set by interleave pattern setting section 108. Interleavepattern setting section 108 is designed to set an interleave pattern inaccordance with channel quality of subcarriers This allows multicarriertransmission apparatus 100 to obtain an effective diversity gaincompared to a case where uniform or random interleave processing isperformed.

The Qch component subjected to the interleave processing by interleaver106 is sent to IQ combination section 105. IQ combination section 105restores a constellation by combining the Ich components and Qchcomponents. In this way, modulation diversity modulation symbols areobtained. The modulation diversity modulation symbols are sent tointerleave information insertion section 109. Interleave informationinsertion section 109 inserts interleave pattern information set byinterleave pattern setting section 108 at a predetermined position of amodulated symbol string.

Modulation diversity modulation symbols and interleave patterninformation are converted to a parallel signal by serial/parallelconversion section (S/P) 110 and a pilot signal is inserted intoparallel signals by pilot signal insertion section 111. The parallelsignal after insertion of pilot signals is subjected to inverse fastFourier transform processing by an inverse fast Fourier transformsection (IFFT). That is, in multicarrier transmission apparatus 100, S/P110 and IFFT 112 as the OFDM modulation section assign each ofmodulation diversity modulation symbols to any one of a plurality ofsubcarriers which are orthogonal to one another and sequentiallymodulate the subcarriers using the modulation diversity modulationsymbols. Radio transmission section 113 applies radio transmissionprocessing such as analog/digital conversion processing andup-conversion to the signal after the IFFT processing and then transmitsthe signal via an antenna.

Multicarrier reception apparatus 200 that performs and demodulates asignal transmitted from multicarrier transmission apparatus 100 includesmodulation diversity demodulation section 201. In multicarrier receptionapparatus 200, radio reception section 202 carries out radio receptionprocessing such as down-conversion and analog/digital conversionprocessing on the radio signal received via an antenna and then sendsthe signal to fast Fourier transform section (FFT) 203. FFT section 203extracts a signal superimposed on subcarriers. The signal extracted fromsubcarriers is sent to pilot signal extraction section 204. Pilot signalextraction section 204 extracts pilot signals of the subcarriers andsends them to propagation path state estimation section 206 and sendsthe modulation diversity modulation symbols arranged on the subcarriersto parallel/serial conversion section (P/S) 205.

P/S 205 sends the signal after the parallel/serial conversion processingto interleave information extraction section 207. Interleave informationextraction section 207 extracts interleave pattern information signalfrom the input signal and sends this information to deinterleaver 209 ofmodulation diversity demodulation section 201.

IQ separation section 208 separates Ich components and Qch components ofthe reception symbols (that is, modulation diversity modulation symbols)and directly sends the Ich components to IQ combination section 210 andsends the Qch components to deinterleaver 209. Deinterleaver 209deinterleaves the Qch components using an interleave patterncorresponding to the interleave pattern information extracted byinterleave information extraction section 207 and then sends them to IQcombination section 210. IQ combination section 210 obtains symbolsbefore interleaving by combining the Ich components and thedeinterleaved Qch components.

Phase rotation section 211 rotates the phase of the Ich components andQch components of the symbols by the same angles as that of phaserotation section 103 on the transmitting side in an opposite directionand thereby restores the phase rotation to its original state. Demappingsection 212 obtains the received data by demodulating the symbols withrestored phases.

Propagation path state estimation section 206 estimates channel qualityof subcarriers based on pilot data arranged on subcarriers. In thisembodiment, a scaling factor for subcarriers is obtained as channelquality of subcarriers using reception pilot data and a pilot replica.

The channel quality information of subcarriers obtained by propagationpath state estimation section 206 is feed back to ranking section 107 ofmulticarrier transmission apparatus 100. In practice, multicarriertransmission apparatus 100 includes a reception section (not shown) asdescribed above and multicarrier reception apparatus 200 includes atransmission section (not shown) Channel quality information transmittedby radio from the transmission section (not shown) of multicarrierreception apparatus 200 to the reception section (not shown) ofmulticarrier transmission apparatus 100 is input to ranking section 107of multicarrier transmission apparatus 100 of the radio station.

Ranking section 107 temporarily stores channel quality information ofsubcarriers, ranks subcarrier numbers in descending order or ascendingorder of channel quality and sends the ranking information to interleavepattern setting section 108. Interleave pattern setting section 108 setsan interleave pattern such that the sum of the above described rankingsof the subcarriers to which the Ich components and Qch components ofsymbols before interleaving are assigned is equal among the respectivesymbols.

Interleave pattern setting section 108 will be explained morespecifically. Since interleave pattern setting section 108 knows inadvance to which subcarrier the Ich component of the symbol mapped bymapping section 102 is to be assigned, it calculates subcarrier numberNq to which Q component RSq of symbol RS is assigned based on thefollowing Expression:Nq=subN(M−R(Ni))   (1)where S is a mapped symbol, RS is a symbol after phase rotationprocessing, RSi, RSq are the Ich component and Qch component thereofrespectively.

In Expression (1), Ni denotes a subcarrier number to which the Ichcomponent is assigned, R(x) denotes ranking of channel quality of asubcarrier of subcarrier number x (scaling factor in this embodiment),subN(y) denotes a subcarrier number whose channel quality ranking is ythand M denotes the total number of ranked subcarriers. This allows thesum of the ranking of a subcarrier to which the Ich component isassigned and the ranking of a subcarrier to which the Qch component isassigned to be kept constant among symbols.

Next, the operations of multicarrier transmission apparatus 100 andmulticarrier reception apparatus 200 configured as shown above will beexplained using FIG. 4, FIG. 5A and FIG. 5B. As shown in FIG. 4, a firsttransmission is performed from multicarrier transmission apparatus 100to multicarrier reception apparatus 200. At the time of this firsttransmission, propagation path information (channel quality ofsubcarriers) is unknown, and therefore, interleave pattern settingsection 108 sets an appropriate interleave pattern for transmission.However, suppose this interleave pattern is known to multicarrierreception apparatus 200. At the first transmission, it is also possibleto send only a pilot signal instead of sending transmission data.

Upon reception of the first transmission signal, multicarrier receptionapparatus 200 extracts the pilot signal placed on subcarriers andpropagation path state estimation section 206 compares the extractedpilot signal with the pilot replica stored beforehand and obtainspropagation path information for subcarriers (channel qualityinformation). Multicarrier reception apparatus 200 then transmits thischannel quality information for subcarriers to multicarrier transmissionapparatus 100 as feedback information.

At the time of a second transmission, multicarrier transmissionapparatus 100 carries out interleave processing on the Qch componentusing an interleave pattern according to the channel quality informationfor each fed back subcarrier and obtainss modulation diversitymodulation symbols. Using the modulation diversity modulation symbols,multicarrier transmission apparatus 100 performs OFDM modulationprocessing and carries out the second transmission.

Upon reception of the second transmission signal, multicarrier receptionapparatus 200 carries out modulation diversity demodulation processingon the received signal and obtains received data. At this time, sincethe modulation diversity modulation symbols received at the second timeare created using an interleave pattern according to channel quality ofsubcarriers, they can obtain an effective diversity gain compared to themodulation diversity modulation symbols received at the first time andthe error correction rate characteristic of the received data improves.

Likewise, multicarrier reception apparatus 200 feeds back the channelquality information of subcarriers estimated using the pilot signal whenthe second transmission signal is received to multicarrier transmissionapparatus 100 and multicarrier transmission apparatus 100 performsmodulation diversity modulation using a new interleave pattern accordingto the channel quality information and carries out a third transmission.

Thus, multicarrier transmission apparatus 100 and multicarrier receptionapparatus 200 adaptively change an interleave pattern of modulationdiversity modulation/demodulation, and can thereby assign Qch to asubcarrier of bad channel quality when Ich is assigned to a subcarrierof good channel quality and assign Qch to a subcarrier of good channelquality when Ich is assigned to a subcarrier of bad channel quality andthereby obtain an effective diversity gain even if a propagation pathcondition changes.

Next, the reason why an effective diversity gain can be obtained ifmodulation diversity modulation is performed using an interleave patternaccording to channel quality of subcarriers as in the case of thisembodiment will be explained using FIG. 5A, FIG. 5B, FIG. 6, FIG. 7 andFIG. 8.

FIG. 5A shows a propagation path variation of subcarriers and FIG. 5Billustrates scaling factors of subcarriers, ranking result of thescaling factor by ranking section 107, assignment of an Ich component tosubcarriers, assignment of a Qch component to subcarriers throughinterleaving of this embodiment and assignment of a Qch component tosubcarriers through conventional interleaving (interleave with twosubcarriers shifts) when subcarriers changes as shown in FIG. 5A.

As is evident from FIG. 5B, the sum of scaling factors of mutuallycorresponding Ich component and Qch component is kept constant in theinterleaving of this embodiment. For example, the ranking of the scalingfactor of I component i₁ of symbol S1 is 1 and the ranking of Qcomponent q₁ is 4, and therefore the sum is 5. On the other hand, theranking of the scaling factor of I component i₂ Of symbol S2 is 4 andthe ranking of Q component q₂ is 1, and therefore the sum is 5. In thisway, an average modulation diversity gain can be obtained with allsymbols, and therefore it is possible to eliminate symbols havingextremely bad error correction rate characteristics.

FIG. 6 shows a signal point position when mapping section 102 carriesout BPSK (Binariphase Phase Shift Keying) processing and phase rotationsection 103 carries out phase rotation processing by 45°.

Furthermore, FIG. 7 shows a signal point position when the symbol inFIG. 6 is subjected to modulation diversity modulation processingwhereby the Ich component is assigned to subcarrier #1 and the Qchcomponent is assigned to subcarrier #2 in the configuration of thisembodiment, transmitted by radio, received and demapped. The distancebetween signal points D in this case can be calculated by the followingexpression:D=2√{square root over (Ci ² +Cq ² )}  (2)

where, Ci in Expression (2) is a scaling factor of the subcarrier towhich Ich is assigned and Cq is a scaling factor of the subcarrier towhich Qch is assigned.

As an example, distances between signal points D₁ to D₄ during demappingis calculated when 4 symbols S₁ to S₄ obtained by mapping as shown inFIG. 6 and expressed by the following expression are transmitted throughthe propagation paths shown in FIG. 5A.S ₁ =i ₁ +jq ₁S ₂ =i ₂ +jq ₂S ₃ =i ₃ +jq ₃S ₄ =i ₄ +jq ₄   (3)

Distances between signal points D₁ to D₄ during demapping of symbols S₁to S₄ when interleaving is performed in the configuration of thisembodiment are expressed by the following expression:D ₁=2√{square root over (5² +1 ² )}=2√{square root over (26)}D ₂=2√{square root over (1² +5 ² )}=2√{square root over (26)}D ₃=2√{square root over (3² +2 ² )}=2√{square root over (13)}D ₄=2√{square root over (2² +3 ² )}=2√{square root over (13)}  (4)

On the other hand, distances between signal points D₁ to D₄ duringdemapping of symbols S₁ to S₄ when an interleaver with 2 subcarriershifts is used as a conventional example are expressed by the followingexpression:D ₁=2√{square root over (5² +3 ² )}=2√{square root over (34)}D ₂=2√{square root over (1² +2 ² )}=2√{square root over (5)}D ₃=2√{square root over (3² =5 ² )}=2√{square root over (34)}D ₄=2√{square root over (2² +1 ² )}=2√{square root over (5)}  (5)

As is clear from a comparison between Expression (4) and Expression (5),it is appreciated that using different interleave patterns according tochannel quality of subcarriers as in the case of this embodiment makesit possible to secure distances between signal points averagely morethan using a fixed interleave pattern.

Next, it is assumed that Gaussian noise of average noise power N isadded to all subcarriers, average error rate Pe of 4 symbols wheninterleaving is performed in the configuration of this embodiment isexpressed by the following expression. erfc in the following expressiondenotes a Gaussian error function. $\begin{matrix}\begin{matrix}{{Pe} = {\frac{1}{4}\left( {{\frac{1}{2}{erfc}\quad\left( \frac{D_{1}}{\sqrt{2N}} \right)} + {\frac{1}{2}{erfc}\quad\left( \frac{D_{2}}{\sqrt{2N}} \right)} + {\frac{1}{2}{erfc}}} \right.}} \\\left. {\left( \frac{D_{3}}{\sqrt{2N}} \right) + {\frac{1}{2}{erfc}\quad\left( \frac{D_{4}}{\sqrt{2N}} \right)}} \right) \\{= {\frac{1}{4}\left( {{{erfc}\quad\left( \frac{2\sqrt{26}}{\sqrt{2N}} \right)} + {{erfc}\quad\left( \frac{2\sqrt{13}}{\sqrt{2N}} \right)}} \right)}} \\{= {\frac{1}{4}\left( {{{erfc}\quad\left( \frac{\sqrt{52}}{\sqrt{N}} \right)} + {{erfc}\quad\left( \frac{\sqrt{26}}{\sqrt{N}} \right)}} \right)}}\end{matrix} & (6)\end{matrix}$

On the other hand, average error rate Pe of 4 symbols when aninterleaver with 2 subcarrier shifts is used as a conventional exampleis expressed by the following expression: $\begin{matrix}\begin{matrix}{{Pe} = {\frac{1}{4}\left( {{\frac{1}{2}{erfc}\quad\left( \frac{D_{1}}{\sqrt{2\quad N}} \right)} + {\frac{1}{2}{erfc}\quad\left( \frac{D_{2}}{\sqrt{2\quad N}} \right)} + {\frac{1}{2}{erfc}}} \right.}} \\\left. {\left( \frac{D_{3}}{\sqrt{2\quad N}} \right) + {\frac{1}{2}{erfc}\quad\left( \frac{D_{4}}{\sqrt{2\quad N}} \right)}} \right) \\{= {\frac{1}{4}\left( {{{erfc}\quad\left( \frac{2\quad\sqrt{34}}{\sqrt{2\quad N}} \right)} + {{erfc}\quad\left( \frac{2\quad\sqrt{5}}{\sqrt{2\quad N}} \right)}} \right)}} \\{= {\frac{1}{4}\left( {{{erfc}\quad\left( \frac{\sqrt{68}}{\sqrt{N}} \right)} + {{erfc}\quad\left( \frac{\sqrt{10}}{\sqrt{N}} \right)}} \right)}}\end{matrix} & (7)\end{matrix}$

FIG. 8 shows average error rate Pe in Expression (6) and Expression (7)when average noise power N as a parameter is changed between 0 and 20dB. From FIG. 8, it is appreciated that the average error rate of thisembodiment (solid line in the figure) drastically improves compared tothe conventional example (dotted line in the figure).

Thus, this embodiment adaptively changes an interleave pattern ofmodulation diversity modulation according to channel quality ofsubcarriers, and therefore it is possible to obtain diversity gainsuniformly for all symbols and improve the error correction ratecharacteristic.

Embodiment 2

FIG. 9 in which parts corresponding to those in FIG. 3 are shown withthe same reference numerals assigned shows the configurations ofmulticarrier transmission apparatus 300 and multicarrier receptionapparatus 400 that receives and demodulates a signal from multicarriertransmission apparatus 300 according to Embodiment 2.

Multicarrier transmission apparatus 300 has a configuration similar tothat of multicarrier transmission apparatus 100 according to Embodiment1 except in that it has a different configuration of interleave patternsetting section 301 and includes interleave pattern table 302.Furthermore, multicarrier reception apparatus 400 has a configurationsimilar to that of multicarrier reception apparatus 200 according toEmbodiment 1 except in that it includes interleave pattern table 401.

Here, interleave pattern table 302 of multicarrier transmissionapparatus 300 stores a plurality of interleave patterns. Interleavepattern setting section 301 sequentially reads a plurality of interleavepatterns stored in interleave pattern table 302 and performs asimulation using interleave patterns and channel quality of subcarriersand thereby selects an interleave pattern which obtains an optimummodulation diversity effect from among the plurality of interleavepatterns.

Then, interleave pattern setting section 301 transmits the selectedinterleave pattern to interleaver 106. Interleaver 106 carries outinterleave processing using set interleave pattern 106. Furthermore,interleave pattern information set by interleave pattern setting section301 is inserted into a transmission signal by interleave informationinsertion section 109 and sent to multicarrier reception apparatus 400.

Interleave pattern table 401 of multicarrier reception apparatus 400stores interleave patterns similar to the interleave patterns stored ininterleave pattern table 302 of multicarrier transmission apparatus 300.Multicarrier reception apparatus 400 reads the same interleave patternas the interleave pattern used on the transmitting side from interleavepattern table 401 based on the interleave pattern information extractedat interleave information extraction section 207 and sends theinterleave pattern to deinterleaver 209. In this way, deinterleaver 209restores Qch components to their original array.

Here, the configuration of interleave pattern setting section 301 ofthis embodiment is shown in FIG. 10. Interleaver 303 reads an interleavepattern stored in interleave pattern table 302 and performs interleavingin the interleave pattern according to which propagation path stateestimation information (that is, channel quality of subcarriers) isread.

In addition section 304, channel quality of interleaved subcarriers andchannel quality of non-interleaved subcarriers are input and, by addingup these channel qualities in subcarrier units, a value is obtained thatis corresponding to summing of Qch components and Ich components insymbol units that are affected by propagation path variations whentransmitted by radio in the current propagation path.

This will be explained more specifically. For example, when the numberof subcarriers is 4, suppose S=(S1,S2,S3,S4) is input as propagationpath state estimation information (channel quality of subcarriers).Suppose an output of S′=(S2,S4,S3,S1) is obtained as a result of usingan interleave pattern from interleaver 303. At this time, abovedescribed S predicts reception power of the Ich component and abovedescribed S′ predicts reception power of the Qch component. Additionsection 304 then performs a vector addition of above described S and S′as shown in the following expression and calculates an absolute valuethereof. $\begin{matrix}\begin{matrix}{S^{''} = {{S + {jS}^{\prime}}}} \\{{= \left. \sqrt{}\left( {{S\quad 12} + {S\quad 22}} \right) \right.},\left. \sqrt{}\left( {{S\quad 22} + {S\quad 42}} \right) \right.,} \\{\left. \sqrt{}\left( {{S\quad 32} + {S\quad 32}} \right) \right.,\left. \sqrt{}\left( {{S\quad 42} + {S\quad 12}} \right) \right.}\end{matrix} & (8)\end{matrix}$

Variance calculation section 305 calculates variance values of all addedelements. More specifically, variances of the four signals of Expression(8) are calculated. The calculated variance values and interleavepattern numbers at that moment are stored in storage section 306. Thatis, storage section 306 stores variance values when interleave patternsstored in interleave pattern table 302 is used, in association with thecorresponding interleave pattern number. Minimum value calculationsection 307 calculates a minimum variance value out of variance valuesstored in storage section 306 and sends the interleave pattern numbercorresponding to the variance value to interleaver 106 and interleaveinformation insertion section 109.

Next, the operation of this embodiment will be explained. Interleaver303 reads an interleave pattern of interleave pattern of number 1 frominterleave pattern table 302 first. Interleaver 303 interleaves channelquality of subcarriers in the read interleave pattern and sends theinterleave result to addition section 304. Addition section 304 adds upchannel quality of subcarriers and interleaved channel quality elementby element (subcarrier by subcarrier). Here, wheb N subcarriers areassumed to be used, an addition results are also N. Variance calculationsection 305 calculates variance values of N addition results. Storagesection 306 stores the variance values in association with theinterleave pattern numbers used to calculate the variance values.Interleave pattern setting section 301 carries out this processing onall interleave patterns by sequentially using interleave patterns storedin interleave pattern table 302.

Interleave pattern setting section 301 finally calculates the minimumvariance value out of variance values stored in storage section 306 byminimum value calculation section 307 and selects an interleave patternnumber corresponding to the variance value.

By so doing, it is possible to select an interleave pattern whereby thesum of channel qualities (e.g., scaling factors) of subcarriers to whichIch components are expected to be assigned and channel qualities ofsubcarriers to which Qch components after being interleaved are expectedto be assigned fluctuates little among symbols. As a result, an averagemodulation diversity gain can be obtained among all symbols, andtherefore symbols having extremely bad error correction ratecharacteristics can be eliminated. More specifically, it is possible toselect an interleave pattern with a high probability of assigning Qchcomponents to subcarriers of bad channel quality when Ich components areassigned to subcarriers of good channel quality and assigning Qch tosubcarriers of good channel quality when Ich components are assigned tosubcarriers of bad channel quality.

Thus, this embodiment provides interleave pattern table 302 storing aplurality of interleave patterns, performs a simulation using storedinterleave patterns and channel quality of subcarriers and can therebyselect an interleave pattern whereby an optimum modulation diversityeffect can be obtained from among the plurality of interleave patterns,and therefore, it is possible to obtain an effective diversity gain andimprove the error correction rate characteristic.

Furthermore, since the receiving side is provided with interleavepattern table 401 storing the same interleave patterns as those ofinterleave pattern table 302 on the transmitting side, it is possiblefor the receiving side to perform deinterleave processing correspondingto an interleave pattern on the transmitting side by only reporting aninterleave pattern number used on the transmitting side and therebyreduce the amount of interleave information to be reported from thetransmitter to the receiver.

Embodiment 3

FIG. 11 in which parts corresponding to those in FIG. 9 are shown withthe same reference numerals assigned shows the configuration ofmulticarrier transmission apparatus 500 and multicarrier receptionapparatus 400 that receives and demodulates a signal from multicarriertransmission apparatus 500 according to Embodiment 3.

Multicarrier transmission apparatus 500 has a configuration similar tothat of multicarrier transmission apparatus 300 of Embodiment 2 exceptin that the configuration of interleave pattern setting section 501 isdifferent. Furthermore, multicarrier reception apparatus 400 has aconfiguration similar to that of multicarrier reception apparatus 400explained in Embodiment 2.

Interleave pattern setting section 501 is similar to interleave patternsetting section 301 in Embodiment 2 in that it sequentially reads aplurality of interleave patterns stored in interleave pattern table 302,performs a simulation using interleave patterns and channel quality ofsubcarriers and thereby selects an interleave pattern whereby an optimummodulation diversity effect can be obtained from the plurality ofinterleave patterns. However, interleave pattern setting section 501 hasa different configuration from interleave pattern setting section 301.

FIG. 12 shows the configuration of interleave pattern setting section501 of this embodiment. Interleaver 502 reads an interleave patternstored in interleave pattern table 302 and interleaves propagation pathstate estimation information (that is, channel quality of subcarriers)in the read interleave pattern.

Subtraction section 503 receives channel quality of interleavedsubcarriers and channel quality of non-interleaved subcarriers andsubtraction section 503 performs subtractions between the channelqualities in subcarrier units, thereby interleaves Qch components in theread interleave pattern and obtains values corresponding to subtractionsin symbol units between the Qch components and Ich components which havebeen affected by variations in the propagation path during radiotransmission through the current propagation path.

Absolute value addition section 504 calculates absolute values of allsubtracted elements and calculates an addition value thereof. Theaddition values of absolute values calculated and the interleave patternnumber at that moment are stored in storage section 505. That is,storage section 505 stores addition values of absolute values wheninterleave patterns stored in interleave pattern table 302 is used inassociation with the corresponding interleave pattern number. Maximumvalue calculation section 506 calculates a maximum value out of theaddition values of absolute values stored in storage section 505 andsends an interleave pattern number corresponding to the addition valueof absolute values to interleaver 106 and interleave informationinsertion section 109.

Next, the operation of this embodiment will be explained.

First, interleaver 502 reads an interleave pattern of interleave patternnumber 1 from interleave pattern table 302. Interleaver 502 interleaveschannel quality of subcarriers in the read interleave pattern and sendsthe interleave result to subtraction section 503. Subtraction section503 performs subtractions in element units (in subcarrier units) betweenchannel qualities of subcarriers and interleaved channel qualities.Here, when N subcarriers are assumed to be used, subtraction results arealso N. Absolute value addition section 504 calculates a total additionvalue after taking the absolute values of N subtraction results. Storagesection 505 stores the addition value of absolute values in associationwith the interleave pattern number used to calculate the addition valueof absolute values. Interleave pattern setting section 501 carries outthis processing repeatedly on all interleave patterns by sequentiallyusing the interleave patterns stored in interleave pattern table 302.

Interleave pattern setting section 501 finally calculates the minimumvalue out of the addition values of absolute values stored in storagesection 505 by maximum value calculation section 506 and selects aninterleave pattern number corresponding to that addition value ofabsolute values.

By so doing, it is possible to select an interleave pattern whereby thedifferences between channel qualities (e.g., scaling factors) ofsubcarriers to which Ich components are expected to be assigned andchannel qualities of subcarriers to which Qch components after beinginterleaved are expected to be assigned increase averagely. As a result,large modulation diversity gains can be obtained averagely for allsymbols, and therefore symbols having extremely bad error correctionrate characteristics can be eliminated. More specifically, it ispossible to select an interleave pattern with a high probability ofassigning Qch components to subcarriers of bad channel quality when Ichcomponents are assigned to subcarriers of good channel quality andassigning Qch to subcarriers of good channel quality when Ich componentsare assigned to subcarriers of bad channel quality.

Thus, according to this embodiment, interleave pattern table 302 storinga plurality of interleave patterns is provided, a simulation usingstored interleave patterns and channel quality of subcarriers isperformed and thereby an interleave pattern whereby an optimummodulation diversity effect can be obtained from among the plurality ofinterleave patterns can be selected, and therefore, it is possible toobtain an effective diversity gain and improve the error correction ratecharacteristic.

Furthermore, since the receiving side is provided with interleavepattern table 401 storing the same interleave patterns as those ofinterleave pattern table 302 on the transmitting side, it is possiblefor the receiving side to perform deinterleave processing correspondingto an interleave pattern on the transmitting side by only reporting aninterleave pattern number used on the transmitting side and therebyreduce the amount of interleave information to be reported from thetransmitter to the receiver.

Embodiment 4

This embodiment proposes a method of reducing channel qualityinformation about information about subcarriers (scaling factor and SNRor the like) to be reported from a receiver to a transmitter. In abovedescribed Embodiments 1 to 3, determining an interleave pattern at thetransmitter (multicarrier transmission apparatus) requires the receiver(multicarrier reception apparatus) to report channel quality ofsubcarriers. It is preferable that this feedback information ispreferably small from the standpoint of radio resources. Thus, thisembodiment proposes several methods of reducing the feedbackinformation. Note that in the following examples, cases where SNR isused as channel quality of subcarriers will be explained.

(1) Method of Reducing Amount of Data 1

SNRs between adjacent subcarriers generally have a high level ofcorrelativity. Therefore, if a subcarrier group is created and one pieceof channel quality information (e.g., SNR) is sent to the subcarriergroup as feedback information, it is possible to effectively reduce theamount of feedback data without deteriorating information aboutsubcarriers so much. For example, when a communication is in progressusing 512 subcarriers, if 16 subcarriers are assumed to form onesubcarrier group, it require only 48 (512÷16=48) SNRs to be fed back.Here, when one piece of channel quality information is fed back fromsubcarrier groups, it is possible to consider using, for example, anaverage SNR of the subcarriers within the group.

However, since the correlativity between adjacent subcarriers depends ona delay spread, when the delay spread is large, the correlativity is lowand when the delay spread is small, the correlativity is high.Considering this fact, it is further preferable not to fix the number ofsubcarriers per subcarrier group and change it depending on a delayspread because it is possible to thereby report more accurate channelquality (SNR) while suppressing the amount of feedback data. Forexample, when a delay spread is large, the correlativity betweenadjacent subcarriers is small, and therefore the number of subcarriersin a subcarrier group is decreased. On the other hand, when the delayspread is small, the correlativity between adjacent subcarriers is high,and therefore the number of subcarriers in the subcarrier group isincreased.

Here, the explanations have been so far focused on the case where SNRsare sent as channel quality information, but when rankings ofsubcarriers are sent, it is possible to determine rankings aftercalculating one SNR per subcarrier group and perform feedbacktransmission in the same way.

(2) Method of Reducing Amount of Data 2

When SNR values are reported in subcarrier units, SNRs may becategorized into a number of layers (classes) and those layers may bereported. For example, as shown in FIG. 13A, SNR values of respectivesubcarriers are categorized using two threshold SNR values (threshold A,threshold B). Instead of the SNR values of the respective subcarriers,area numbers classified as shown in FIG. 13B are reported to atransmitter as feedback information.

This can reduce the amount of feedback information compared to the casewhere SNR values of respective subcarriers are directly transmitted tothe transmitter as feedback information.

(3) Method of Reducing Amount of Data 3

When feedback data is reported, ranking orders of SNRs are reportedinstead of measured SNR values of respective subcarriers. For example,when SNR values of respective subcarriers measured at a receiver are asshown in FIG. 14A, subcarrier numbers in descending order of channelconditions are reported as feedback information as shown in FIG. 14B.

Furthermore, when SNR ranking orders are reported in this way,subcarrier numbers of subcarriers whose SNR values are lower than athreshold may not be included in the feedback information. By so doing,a multicarrier transmitter (downlink transmitter) recognizes thesubcarriers whose numbers have not been reported and does not assign anydata to the subcarriers, and can thereby avoid data from being assignedto subcarriers having very low channel quality and prevent unnecessarydata transmission. As a result, it is possible to reduce unnecessarytransmit power.

For example, when SNR values of respective subcarriers measured by thereceiver are as shown in FIG. 15A, the subcarrier number of subcarrier#4 whose SNR value is lower than threshold C may not be reported asfeedback information as shown in FIG. 15B. The multicarrier transmitterthat has acquired the feedback information sets an interleave pattern bythe interleave pattern setting section in such a way that no data isassigned to the subcarrier of subcarrier number #6 which is not includedin the feedback information.

Furthermore, when SNR rankings are reported, it is also possible toclassify the SNR values as shown in FIG. 16A to FIG. 16D, not to includesubcarriers having medium level of SNRs in the feedback information andfeed back subcarrier numbers in descending order of SNR values asfeedback information 1 and feed back subcarrier numbers in ascendingorder of SNR values as feedback information 2. In the examples in FIG.16A to FIG. 16D, SNR values are classified into three classes usingthreshold D and threshold E (FIG. 16A), subcarrier #1, #10, #8, #4 whoseSNRs are medium level are not included in the feedback information (FIG.16D), subcarrier numbers #3, #2, #9 in descending order of SNRs are fedback as feedback information 1 (FIG. 16B) and subcarrier numbers inascending order of SNRs are fed back as feedback information 2 (FIG.16C).

The multicarrier transmitter that receives this feedback informationacquires subcarrier numbers in descending order of SNRs from feedbackinformation 1 as shown in FIG. 17 and acquires subcarrier numbers inascending order of SNRs from feedback information 2, and the interleavepattern setting section sets an adaptive interleave patterncorresponding to channel quality as the interleave pattern ofsubcarriers to which Ich and Qch are assigned as explained in Embodiment1 for these subcarriers (that is, subcarriers whose channel quality ishigh or low) and thereby carries out adaptive interleaving according tochannel quality of subcarriers. The multicarrier transmitter carries outrandom interleaving for other subcarrier numbers whose SNR values aremedium level by setting a random interleave pattern through theinterleave pattern setting section.

Here, threshold D and threshold E are preferably set to SNR values (0 dBand 6 dB in this case) on a boundary when the effects of diversity gainsare divided into a high area and low area as shown in FIG. 18 (shows SNRvalues on the horizontal axis and probability densities of SNR values ofrespective subcarriers on the vertical axis). By so doing, it ispossible to reduce the amount of feedback data for the intermediate SNRarea where diversity effects are not obtained so much even if feedbackis performed (that is, adaptive interleaving is performed).

Furthermore, when, for example, control information that the amount offeedback data should be reduced is received from the multicarriertransmitter, above described threshold D is decremented by 1 dB andthreshold E is incremented by 1 dB. By so doing, it is possible toperform feedback for only the areas where effects of diversity gains arehigh. On the contrary, when control information that the amount offeedback data can be increased is received, above described threshold Dis incremented by 1 dB and threshold E is decremented by 1 dB. By sodoing, it is possible to increase more effective feedback data and as aresult, it is possible to design an adaptive interleaver using morefeedback data.

(4) Method of Reducing Feedback Count

When a plurality of temporally intermittent frames (packets) aretransmitted, the present invention proposes to change transmissionintervals of feedback data according to a Doppler frequency instead oftransmitting feedback data in frame units.

A temporal variation of SNR values is proportional to a Dopplerfrequency (relative moving speed between a receiver and a transmitter).That is, when the Doppler frequency is low, a temporal variation of SNRvalues is estimated to be small and when the Doppler frequency is high,a temporal variation of SNR values is estimated to be large. Inconsideration of this, when the Doppler frequency is low, the sameinterleave pattern is used without transmitting feedback data for aperiod of several frames and transmit, and when the Doppler frequency ishigh, feedback data for every frame is transmitted and the interleavepattern is updated.

Here, a case where SNRs are sent is explained, but the present inventionis likewise applicable to a case where SNR rankings of subcarriers orinterleaver table numbers are reported.

FIG. 19 shows an example of the frequency of transmitting feedback dataand switching between the interleave methods according to thisembodiment. As shown in the figure, at a Doppler frequency fD of 20 Hzor below, changing the frequency of transmitting feedback data producessubstantially no characteristic difference (PER (Packet Error Rate) inthe figure). Therefore, in such a case, the amount of feedback data isreduced by reducing the frequency of transmitting feedback data (onceevery three frames in the figure). On the other hand, when Dopplerfrequency fD is 20 Hz to 80 Hz, the characteristic does not deteriorateeven with feedback data once every 2 frames, and therefore feedback datais transmitted once every 2 frames. Furthermore, in an area of Dopplerfrequency fD of 200 Hz or higher, even when feedback data is sent everyframe, almost no effect of characteristic improvement can be expectedcompared to the case where random interleave is performed. Therefore, insuch a case, an instruction to stop transmitting SNR values as feedbackdata, carry out modulation diversity modulation using random interleaveinstead of adaptive interleave is reported to the multicarriertransmitter.

Embodiment 5

This embodiment will explain a configuration in a case where the presentinvention is applied to an OFDM system whereby the same symbol istransmitted a plurality of times repeatedly (hereinafter referred to as“repetition OFDM”) will be explained.

First, the repetition OFDM will be explained briefly.

Transmitting the same symbol repeatedly makes the transmission rate ofrepetition OFDM low, but when, for example, a downlink receptionterminal is located near a cell edge where an SNR value is very bad, itis proposed as an effective system to transmit information reliably.Symbol repetition is designed to transmit symbols such as QPSK and BPSKrepeatedly within the same frame, repeatedly combine the symbols at thereceiving side and make it possible to obtain a diversity effect.

FIG. 20 in which parts corresponding to those in FIG. 3 are shown withthe same reference numerals assigned shows the configuration ofmulticarrier transmission apparatus 600 and multicarrier receptionapparatus 700 that receives and demodulates signals from multicarriertransmission apparatus 600 according to this embodiment.

Multicarrier transmission apparatus 600 is constructed in aconfiguration similar to that of multicarrier transmission apparatus 100according to Embodiment 1 except in that modulation diversity modulationsection 601 is provided with symbol iteration section 602 and Ich, Qchinterleavers 603, 604 and that the configuration of interleaver patternsetting section 605 is different. Symbol iteration section 602 outputssymbols which are sequentially input from mapping section 102 repeatedlya plurality of times. That is, symbol iteration section 602 forms aplurality of the same symbols and outputs them.

Multicarrier reception apparatus 700 is constructed in a configurationsimilar to that of multicarrier reception apparatus 200 according toEmbodiment 1 except in that modulation diversity demodulation section701 is provided with symbol combination section 704 that combines andoutputs the same symbols corresponding to the same iteration countoutput from phase rotation section 211 and Ich, Qch deinterleavers 702,703.

Next, the operations of multicarrier transmission apparatus 600 andmulticarrier reception apparatus 700 will be explained especiallyfocused on the setting operation of an interleave pattern.

First, the operation of multicarrier transmission apparatus 600 will beexplained using FIG. 21. Multicarrier transmission apparatus 600performs the following operation to set interleave patterns ofrespective interleavers 603, 604.

-   (1) Ranking section 107 receives feedback data (SNR values in    subcarrier units) (ST1) and ranks them (ST2).-   (2) Interleave pattern setting section 605 divides SNR value    rankings into odd-number rankings and even-number rankings (ST3,    ST4).-   (3) Even-number ranking is changed upside down (ST5)-   (4) Symbol iteration section 602 forms iteration symbols. Here, when    an iteration count (iteration coefficient) is 2, making two copies    of original symbols S1 and S2 (ST11) forms iteration symbols as    shown in ST12.-   (5) In ST13, an interleave pattern is set using odd-number ranking    for original symbols S1 and S2 as in the case of Embodiment 1 such    that the sum of the odd-number rankings of subcarriers to which Ich    components are assigned and the odd-number rankings of subcarriers    to which Qch components are assigned is constant between symbols S1    and S2. More specifically, interleave patterns of Ich, Qch    interleavers 603, 604 are set so that S1(Ich) is assigned to    subcarrier #3, S2(Ich) is assigned to subcarrier #1, S1(Qch) is    assigned to subcarrier #7 and S2(Qch) is assigned to subcarrier #4.-   (6) In ST14, an interleave pattern is set using even-number ranking    (ascending order of SNR values) for iteration symbols S1 and S2 as    in the case of Embodiment 1 such that the sum of the even-number    rankings of subcarriers to which Ich components are assigned and the    even-number rankings of subcarriers to which Qch components are    assigned is constant between iteration symbols S1, S2. More    specifically, interleave patterns of Ich, Qch interleavers 603, 604    are set so that S1(Ich) is assigned to subcarrier #6, S2(Ich) is    assigned to subcarrier #5, S1(Qch) is assigned to subcarrier #2 and    S2(Qch) is assigned to subcarrier #8.-   (7) In ST15, a final Ich interleave pattern and Qch interleave    pattern are set by splicing the interleave pattern set in ST13 and    the interleave pattern set in ST14 with each Ich and Qch. More    specifically, the interleave pattern for original symbol Ich created    in ST13 and the interleave pattern for iteration symbol Ich created    in ST14 are spliced together into one Ich interleave pattern.    Likewise, the interleave pattern for original symbol Qch created in    ST13 and the interleave pattern for iteration symbol Qch created in    ST14 are spliced together into one Qch interleave pattern.

By setting such interleave patterns, symbol combination section 704 ofmulticarrier reception apparatus 700 obtains reception constellations asshown in FIG. 22. In these constellations, a distance between signalpoints is kept wide especially in the constellation after thecombination, and therefore the minimum value of the distance betweensignal points which has a maximum influence on the BER characteristicincreases and the BER characteristic improves.

This embodiment explains the case where interleave pattern of originalsymbols S1, S2 and on their iteration symbols are uniquely determinedbased on the channel quality rankings of subcarriers, but the presentinvention is not limited to this and it is also possible to set anadaptive interleave pattern through an advance simulation at thetransmitter to determine to which subcarriers Ich and Qch of theoriginal symbols and iteration symbols should be assigned fortransmission so that the minimum value of the distance between signalpoints of the constellation after the combination increases averagely atthe receiver.

An example of the operation of multicarrier transmission apparatus 600in such a case will be explained using FIG. 23.

-   (1) Ranking section 107 receives feedback data (SNR values in    subcarrier units) (ST1) and ranks the feedback data (ST2).-   (2) Interleave pattern setting section 605 divides SNR value    rankings into odd-number rankings and even-number rankings (ST3,    ST4).-   (3) Symbol iteration section 602 forms iteration symbols (ST21).-   (4) In ST22, using an order of odd-number rankings for a    phase-rotated QPSK constellation as in the case of Embodiment 1, a    combination is created such that the sum of odd-number rankings of    subcarriers to which Ich components are assigned and odd-number    rankings of subcarriers to which Qch components are assigned becomes    constant. In this example, there are four combinations whereby the    sum of odd-number rankings becomes constant. More specifically, the    following four combinations are created. These combinations are    created for all the four phase rotated QPSK signals.-   Combination A: Ich of a symbol is assigned to subcarrier #3 and Qch    is assigned to subcarrier #7.-   Combination B: Ich of a symbol is assigned to subcarrier #1 and Qch    is assigned to subcarrier #4.-   Combination C: Ich of a symbol is assigned to subcarrier #4 and Qch    is assigned to subcarrier #1.-   Combination D: Ich of a symbol is assigned to subcarrier #7 and Qch    is assigned to subcarrier #3.-   (5) In ST23, using an order of even-number rankings for a    phase-rotated QPSK constellation as in the case of Embodiment 1, a    combination is created such that the sum of even-number rankings of    subcarriers to which Ich components are assigned and even-number    rankings of subcarriers to which Qch components are assigned becomes    constant. More specifically, the following four combinations are    created. These combinations are created for all the four    phase-rotated QPSK signals.-   Combination E: Ich of a symbol is assigned to subcarrier #2 and Qch    is assigned to subcarrier #6.-   Combination F: Ich of a symbol is assigned to subcarrier #8 and Qch    is assigned to subcarrier #5-   Combination G: Ich of a symbol is assigned to subcarrier #5 and Qch    is assigned to subcarrier #8.-   Combination H: Ich of a symbol is assigned to subcarrier #6 and Qch    is assigned to subcarrier #2.-   (6) In ST24, an interleave pattern is set by selecting combinations    A to D for each of four original symbols, selecting any one of    combinations E to H for each of four iteration symbols and    simulating one whereby a minimum value of the distance between    signal points after combining the original symbols and iteration    symbols increases averagely when those combinations are selected.    That is, a combination whereby a minimum value of the distance    between signal points after the combination increases averagely is    selected. For example, combination A is selected for the original    symbols and combination G is selected for the iteration symbols. A    result of splicing these combinations together is set as an    interleave pattern.

In short, the explanations of FIG. 20 to FIG. 23 can be summarized asfollows: Symbol iteration section 602 forms the identical first andsecond symbols for sequentially input symbols and interleave patternsetting section 605 sets an interleave pattern whereby Ich of the firstsymbol and Qch of the second symbol sequentially assigned to subcarriersin descending order of channel quality and Qch of the first symbol andIch of the second symbol are sequentially assigned to subcarriers inascending order of channel quality. This causes the minimum value of thedistance between signal points of a combined symbol of the first symboland second symbol obtained on the receiving side to increase averagely,and therefore it is possible to prevent the bits of the combined symbolfrom including bits of high and low error rates.

This embodiment explains the case where the number of iterations is 2,but even in a case where the number of iterations is 3 or above, it islikewise possible to design an interleave pattern whereby subcarriersare assigned so that the number of subcarriers in a good channelcondition is substantially equal to the number of subcarriers in a badchannel condition when calculated per original symbol and the minimumvalue of distances between signal points of the combined symbol at thereceiver increases averagely.

Other Embodiments

The above described embodiments explain the case where multicarriertransmission apparatuses 100, 300 and 600 set interleave patterns, butthe present invention is not limited to this and interleave patternsetting processing similar to the above described processing may also beperformed on the receiver side and interleave pattern information may bereported instead of propagation path information (channel qualityinformation) as feedback information.

Furthermore, the above described embodiments explains the case where ascaling factor obtained from a variation in a pilot symbol is used aschannel quality, but the present invention is not limited to this and itis possible to apply channel quality obtained by various conventionallyproposed methods as channel quality of subcarriers. For example, it ispossible to detect channel quality of subcarriers based on average powerof data symbols of subcarriers and detect channel quality of subcarriersusing a scaling factor obtained by the method of applying an IFFT to adelay profile and further use an SNR (Signal-to-Noise Ratio) ofsubcarriers as a channel quality value of subcarriers.

Furthermore, above described Embodiment 1 explains the case wherechannel quality of subcarriers is unknown during initial transmission,but if channel quality of subcarriers is known, it is also possible toset an interleave pattern corresponding to channel quality by interleavepattern setting section 108 from the time of initial transmission andperform modulation diversity modulation.

Furthermore, above described Embodiments 1 to 4 explains the case whereQch components are interleaved, but the present invention is not limitedto this and it is also possible to interleave only Ich components orinterleave both Ich components and Qch components and even in such acase, if an interleave pattern is adaptively set according to channelquality of subcarriers as in the case of the above describedembodiments, it is possible to obtain the same effects as the abovedescribed embodiments.

Furthermore, the above described embodiments explains the case wherephase rotation section 103 is provided in addition to mapping section102 and the phases of the I component and Q component are rotated, butthe present invention is not limited to this and if the mapping sectionperforms mapping processing with phase rotation also taken intoconsideration, the phase rotation section may be omitted.

Furthermore, the above described embodiments have explained the casewhere the receiver measures channel quality (scaling factor and SNR orthe like) of subcarriers, transmits the measurement result to thetransmitter as feedback data and the transmitter ranks SNR values,determines an interleave pattern, transmits data subjected to modulationdiversity modulation together with interleave pattern information to thereceiver and the receiver creates a deinterleave pattern from theinterleave pattern information and performs demodulation using thisinterleave pattern. However exchanges of control data between themulticarrier transmission apparatus and multicarrier reception apparatusaccording to the present invention are not limited to this. Someexamples of exchanges of control data other than that of the abovedescribed embodiments will be shown below.

(i) Method of Feeding Back Channel Quality Information

First, the receiver measures channel quality of subcarriers, rankschannel quality of subcarriers, determines a deinterleave pattern andthen stores it. Next, the receiver transmits channel quality informationto the transmitter as feedback data and the transmitter also rankschannel quality based on this and determines an interleave pattern.Then, the transmitter transmits data subjected to modulation diversitymodulation to the receiver. The receiver demodulates the data subjectedto modulation diversity modulation using the stored deinterleavepattern.

(ii) Method of Feeding Back Ranking Data

First, the receiver measures channel quality of subcarriers, rankschannel quality of subcarriers, determines a deinterleave pattern andthen stores it. The receiver then transmits ranking values to thetransmitter as feedback data. The transmitter determines an interleavepattern from the ranking values and transmits data subjected tomodulation diversity modulation to the receiver. The receiverdemodulates the data subjected to modulation diversity modulation usingthe stored deinterleave pattern.

(iii) Method of Feeding Back Delay Profile

First, the receiver measures a delay profile and transmits the delayprofile to the transmitter. Next, the transmitter obtains channelquality values by applying an FFT to the delay profile, ranks them,determines an interleave pattern and the transmitter transmits datasubjected to modulation diversity modulation together with interleavepattern information to the receiver, and the receiver creates adeinterleave pattern from the interleave pattern information andperforms demodulation using this interleave pattern.

(iv) Method of Feeding Back Delay Profile (No.2)

First, the receiver measures a delay profile and obtains channel qualityof subcarriers based on this delay profile, ranks the channel quality,determines a deinterleave pattern and stores it. Next, the receivertransmits the delay profile to the transmitter, and the transmitterapplies an FFT to the delay profile, obtains channel qualities, ranksthem, determines an interleave pattern. The transmitter then transmitsdata subjected to modulation diversity modulation to the receiver. Thereceiver demodulates the data subjected to modulation diversitymodulation using the stored deinterleave pattern.

Furthermore, above described Embodiments 2, 3 explains, as exchanges ofcontrol data when the transmitter and receiver are provided withinterleave pattern tables, the case where the receiver measures channelquality of subcarriers, transmits the measurement result to thetransmitter as feedback data and the transmitter selects an interleavepattern which can obtain a highest diversity gain from among theprestored interleave patterns and transmits data subjected to modulationdiversity modulation together with interleave pattern numbers to thereceiver and the receiver reads the reported interleave pattern from theinterleave pattern table and performs demodulation. However, the presentinvention may also be adapted as follow:

That is, the receiver measures channel quality of subcarriers, thereceiver selects an interleave pattern that can obtain a highestdiversity gain from the interleave pattern table and stores theinterleave pattern number. The receiver transmits the interleave patternnumber to the transmitter as feedback information. The transmitter readsan interleave pattern of the reported interleave pattern number from theinterleave pattern table, performs interleaving and transmits datasubjected to modulation diversity modulation to the receiver.

Furthermore, the above described embodiments explain the case where thereceiver measures channel quality of subcarriers, but depending on theaccess scheme, the transmitter may also measure channel quality ofsubcarriers. By so doing, it is possible to eliminate the necessity oftransmitting channel quality information from the receiver to thetransmitter, and thereby reduce feedback data. For example, a TDD (TimeDivision Duplex) scheme may be used as the access scheme. The TDD schemeis a scheme under which the same frequency band is used on an uplinkchannel and downlink channel and communication is carried out on atime-division basis. That is, the uplink channel has the same channelcondition as that of the downlink channel. Taking advantage of thismakes it possible to reduce feedback data.

For example, as in the case of Embodiment 1, when an interleave patternis determined by ranking channel quality, the transmitter measureschannel quality of subcarriers from received pilot signals or the like,ranks subcarriers based on the channel quality, thereby determines aninterleave pattern, carries out modulation diversity modulation in thedetermined interleave pattern and transmits the data subjected tomodulation diversity modulation and interleave pattern information. Thereceiver performs demodulation using the reported interleave pattern.

Furthermore, when an interleave pattern table is provided as in thecases of Embodiments 2, 3, the transmitter measures channel quality ofsubcarriers from received pilot signals or the like, selects aninterleave pattern that can gain a highest diversity gain from theprestored interleave pattern based on the channel quality, transmitsdata subjected to modulation diversity modulation together withinterleave pattern numbers to the receiver. The receiver reads aninterleave pattern of the reported interleave pattern number from theinterleave pattern table and performs demodulation using this interleavepattern.

Furthermore, the above described embodiments explain the case whereinterleave pattern setting sections 108, 605 set an interleave patternso that the sum of channel quality rankings of subcarriers to which Ichcomponents and Qch components are assigned is equal among symbols.However, it is not necessary that the sum is always be exactly equal,and it is possible to obtain the same effect as the embodiment bysetting an interleave pattern such that the sum of channel qualityranking of subcarriers to which Ich components and Qch components areassigned is averaged among symbols

An aspect of the multicarrier transmission apparatus of the presentinvention adopts a configuration including a symbol formation sectionthat forms symbols made up of Ich components and Qch components fromtransmission data, an interleaver that interleaves the Ich componentsand/or Qch components independently of each other, an IQ combinationsection that combines the interleaved Ich components and Qch componentsto obtain modulation diversity modulation symbols, an OFDM modulationsection that assigns each modulation diversity modulation symbol to anyone of a plurality of subcarriers which are orthogonal to one anotherand modulates subcarriers using the modulation diversity modulationsymbol and an interleave pattern setting section that sets an interleavepattern in the interleaver according to channel quality of subcarriers.

According to this configuration, an interleave pattern of modulationdiversity modulation is adaptively changed according to channel qualityof subcarriers and a good diversity gain can be thereby obtainedaccording to the propagation path characteristic.

Another aspect of the multicarrier transmission apparatus of the presentinvention adopts a configuration further including a ranking sectionthat ranks the channel quality of subcarriers, wherein the interleavepattern setting section sets an interleave pattern such that the sum ofrankings of subcarriers to which Ich components and Qch components ofsymbols before interleaving are assigned is averaged among symbols.

According to this configuration, it is possible to set an interleavepattern such that the sum of channel qualities of Ich components and Qchcomponents is substantially equal among symbols before interleaving. Asa result, diversity gains can be obtained uniformly for all symbols andthe overall error correction rate characteristic can be therebyimproved.

A further aspect of the multicarrier transmission apparatus of thepresent invention adopts a configuration further including an interleavepattern storage section that stores a plurality of interleave patterns,wherein the interleave pattern setting section performs a simulationusing the plurality of interleave patterns and channel quality ofsubcarriers in advance and selects an interleave pattern whereby anoptimum modulation diversity effect can be obtained from among theplurality of interleave patterns as the interleave pattern to be usedfor the interleaver.

According to this configuration, an optimum interleave pattern isselected from among provided interleave patterns and it is therebyeasier to select the interleave pattern. Furthermore, when adeinterleave pattern on the receiving side is reported to the receivingside, only the corresponding interleave pattern number need to betransmitted, and it is possible to thereby reduce the amount oftransmission information.

A still further aspect of the multicarrier transmission apparatus of thepresent invention adopts a configuration, wherein the interleave patternsetting section includes an interleaver that interleaves a channelquality value of subcarriers using an interleave pattern for Ichcomponents and/or interleave pattern for Qch components, an additionsection that adds up interleaved Ich channel quality values and Qchchannel quality values in subcarrier units, a variance calculationsection that calculates a variance value of the addition result and aminimum value calculation section that selects an interleave patternhaving a minimum variance from among the plurality of interleavepatterns.

A still further aspect of the multicarrier transmission apparatus of thepresent invention adopts a configuration, wherein the interleave patternsetting section includes an interleaver that interleaves the channelquality value of subcarriers using an interleave pattern for Ichcomponents and/or an interleave pattern for Qch components, asubtraction section that performs subtractions between the channelquality values of interleaved Ich and channel quality values of Qch insubcarrier units, an absolute value addition section that calculates thesum of absolute values of subtraction results in subcarrier units and amaximum value calculation section that selects the interleave patternhaving the maximum sum of the absolute values from among the pluralityof interleave patterns.

According to these configurations, it is possible to select aninterleave pattern whereby the sum of channel qualities of subcarriersto which Ich components are expected to be assigned and channel qualityof subcarriers to which Qch components are expected to be assigned doesnot change among symbols so much. As a result, it is possible to obtainaverage modulation diversity gains for all symbols.

A still further aspect of the multicarrier transmission apparatus of thepresent invention adopts a configuration, further including aninterleave information insertion section that inserts information aboutthe interleave pattern set by the interleave pattern setting sectioninto a transmission signal.

According to this configuration, the receiving side can accuratelyperform deinterleave processing based on the inserted interleave patterninformation.

A still further aspect of the multicarrier transmission apparatus of thepresent invention adopts a configuration where the interleave patternsetting section sets an interleave pattern whereby the Ich componentsand Qch components are not assigned to subcarriers whose channel qualityis a predetermined value or below.

According to this configuration, symbols are not assigned to subcarriershaving a high probability of symbol errors on the receiving side, and itis possible to thereby reduce unnecessary transmit power.

A still further aspect of the multicarrier transmission apparatus of thepresent invention adopts a configuration, wherein the interleave patternsetting section sets an adaptive interleave pattern according to channelquality of subcarriers for the Ich components and Qch componentsassigned to the subcarriers having high channel quality and low channelquality and sets a random interleave pattern for the Ich components andQch components assigned to the subcarriers having medium channelquality.

According to this configuration, the multicarrier reception apparatusdoes not feed back channel quality information about subcarriers havingmedium channel quality to the multicarrier transmission apparatus, andtherefore it is possible to reduce the amount of feedback informationaccordingly. Note that even an adaptive interleave pattern correspondingto the channel quality is performed for subcarriers having mediumchannel quality, its diversity effect is substantially not differentfrom that of random interleaving. Thus, it is possible to effectivelyreduce the amount of feedback information while maintaining thediversity effect.

A still further aspect of the multicarrier transmission apparatus of thepresent invention adopts a configuration, further including an iterationsymbol formation section that forms identical first and second symbolsfor each of sequentially input symbols, wherein the interleave patternsetting section sets an interleave pattern whereby Ich of the firstsymbol and Qch of the second symbol are sequentially assigned tosubcarriers in descending order of channel quality and Qch of the firstsymbol and Ich of the second symbol are sequentially assigned tosubcarriers in ascending order of channel quality.

According to this configuration, a minimum value of the distance betweensignal points of the combined symbol of the first symbol and secondsymbol obtained on the receiving side increases averagely, and thereforeit is possible to prevent the combined symbol from having bits with ahigh probability of errors and bits with a low probability of errors.

An aspect of the multicarrier reception apparatus of the presentinvention adopts a configuration including an OFDM demodulation sectionthat extracts modulation diversity symbols superimposed on subcarriersof a received multicarrier signal, a deinterleaver that deinterleavesIch components and/or Qch components of modulation diversity modulationsymbols using an interleave pattern according to channel quality ofsubcarriers, an IQ combination section that combines the deinterleavedIch components and Qch components and a demapping section that obtainsreceived data by demapping symbols after the combination.

Another aspect of the multicarrier reception apparatus of the presentinvention adopts a configuration, wherein the deinterleaver performsdeinterleave processing using an interleave pattern based on interleaveinformation transmitted from the transmitting side.

According to these configurations, when the multicarrier transmissionapparatus transmits a signal subjected to modulation diversitymodulation processing with an interleave pattern adaptively changedaccording to channel quality, it is possible to correctly obtainreceived data before modulation from reception modulation diversitysymbols.

A further aspect of the multicarrier reception apparatus of the presentinvention adopts a configuration, further including a propagation pathstate estimation section that obtains channel quality of subcarriers anda transmission section that transmits information indicating the channelquality of subcarriers to the multicarrier transmission apparatus thattransmits a signal on which the modulation diversity modulation symbolsare superimposed, wherein a plurality of adjacent subcarriers aregrouped and one piece of channel quality information per group out ofthe channel quality information of subcarriers is transmitted to themulticarrier transmission apparatus.

A still further aspect of the multicarrier reception apparatus of thepresent invention adopts a configuration, further including apropagation path state estimation section that obtains channel qualityof subcarriers, a transmission section that transmits informationindicating the channel quality of subcarriers to the multicarriertransmission apparatus that transmits a signal on which the modulationdiversity modulation symbols are superimposed and a transmission sectionthat transmits information indicating channel quality of subcarriers tothe reception section of the multicarrier transmission apparatus thattransmits a signal on which the modulation diversity modulation symbolsare superimposed, wherein the transmission section transmits the channelquality information to the multicarrier transmission apparatus atshorter time intervals as a Doppler frequency increases.

A still further aspect of the multicarrier reception apparatus of thepresent invention adopts a configuration, further including apropagation path state estimation section that obtains channel qualityof subcarriers and a transmission section that transmits informationindicating the channel quality of subcarriers to the multicarriertransmission apparatus that transmits a signal on which the modulationdiversity modulation symbols are superimposed, wherein when the Dopplerfrequency equals or exceeds a predetermined value, transmission ofinformation indicating the channel quality of subcarriers to themulticarrier transmission apparatus is stopped.

A still further aspect of the multicarrier reception apparatus of thepresent invention adopts a configuration, further including apropagation path state estimation section that obtains channel qualityof subcarriers and a transmission section that transmits informationindicating the channel quality of subcarriers to the multicarriertransmission apparatus that transmits a signal on which the modulationdiversity modulation symbols are superimposed, wherein the channelquality of subcarriers is classified according to the degree of channelquality and information indicating a class of subcarriers is transmittedto the multicarrier transmission apparatus as information indicating thechannel quality of subcarriers.

According to these configurations, it is possible to report accuratechannel quality information to the multicarrier transmission apparatuswhile suppressing the amount of feedback data or feedback count.

An aspect of the multicarrier communication method of the presentinvention includes a step of detecting channel quality of subcarriersand a modulation diversity modulation step of carrying out modulationdiversity modulation while adaptively changing an interleave pattern ofIch components and/or Qch components according to channel quality ofsubcarriers.

The present invention is not limited to the above described embodimentsbut can be implemented modified in various ways.

As explained so far, according to the present invention, it is possibleto further improve the error correction rate characteristic when amodulation diversity modulation/demodulation technology is applied.

This application is based on Japanese Patent Application No. 2003-274366filed on Jul. 14, 2003, entire content of which is expresslyincorporated by reference herein.

INDUSTRIAL APPLICABILITY

The present invention is widely applicable to radio communicationequipment that carries out modulation diversity modulation/demodulation.

1. A multicarrier transmission apparatus comprising: a symbol formationsection that forms symbols made up of Ich components and Qch componentsfrom transmission data; an interleaver that interleaves said Ichcomponents and/or Qch components independently of each other; an IQcombination section that combines the interleaved Ich components and Qchcomponents and obtains modulation diversity modulation symbols; an OFDMmodulation section that assigns modulation diversity modulation symbolsto any one of a plurality of subcarriers which are orthogonal to oneanother and modulates subcarriers using the modulation diversitymodulation symbols; and an interleave pattern setting section that setsan interleave pattern in said interleaver according to channel qualityof said subcarriers.
 2. The multicarrier transmission apparatusaccording to claim 1, further comprising a ranking section that ranksthe channel quality of said subcarriers, wherein said interleave patternsetting section sets an interleave pattern such that the sum of therankings of subcarriers to which Ich components and Qch components ofsaid symbols before interleaving are assigned is averaged among symbols.3. The multicarrier transmission apparatus according to claim 1, furthercomprising an interleave pattern storage section that stores a pluralityof interleave patterns, wherein said interleave pattern setting sectionperforms a simulation using said plurality of interleave patterns andchannel quality of subcarriers in advance and selects an interleavepattern whereby an optimum modulation diversity effect can be obtainedfrom among said plurality of interleave patterns as the interleavepattern to be used for said interleaver.
 4. The multicarriertransmission apparatus according to claim 1, wherein said interleavepattern setting section comprises: an interleaver that interleaves achannel quality value of said subcarriers using an interleave patternfor Ich components and/or interleave pattern for Qch components; anaddition section that adds up interleaved Ich channel quality values andQch channel quality values in subcarrier units; a variance calculationsection that calculates a variance value of the addition result; and aminimum value calculation section that selects an interleave patternhaving a minimum variance from among the plurality of interleavepatterns.
 5. The multicarrier transmission apparatus according to claim1, wherein said interleave pattern setting section comprises: aninterleaver that interleaves the channel quality value of saidsubcarriers using an interleave pattern for Ich components and/or aninterleave pattern for Qch components; a subtraction section thatperforms subtractions between the channel quality values of interleavedIch and channel quality values of Qch in subcarrier units; an absolutevalue addition section that calculates the sum of absolute values ofsubtraction results in subcarrier units; and a maximum value calculationsection that selects the interleave pattern having a maximum sum of saidabsolute values from among the plurality of interleave patterns. 6.(canceled)
 7. The multicarrier transmission apparatus according to claim1, wherein said interleave pattern setting section sets an interleavepattern whereby said Ich components and Qch components are not assignedto subcarriers whose channel quality is a predetermined value or below.8. The multicarrier transmission apparatus according to claim 1, whereinsaid interleave pattern setting section sets an adaptive interleavepattern according to channel quality of subcarriers for said Ichcomponents and Qch components assigned to said subcarriers having highchannel quality and low channel quality and sets a random interleavepattern for said Ich components and Qch components assigned to saidsubcarriers having medium channel quality.
 9. The multicarriertransmission apparatus according to claim 1, further comprising aniteration symbol formation section that forms identical first and secondsymbols for sequentially input symbols, wherein said interleave patternsetting section sets an interleave pattern whereby Ich of said firstsymbol and Qch of said second symbol are sequentially assigned tosubcarriers in descending order of channel quality and Qch of said firstsymbol and Ich of said second symbol are sequentially assigned tosubcarriers in ascending order of channel quality.
 10. A multicarrierreception apparatus comprising: an OFDM demodulation section thatextracts modulation diversity symbols superimposed on subcarriers of areceived multicarrier signal; a deinterleaver that deinterleaves Ichcomponents and/or Qch components of said modulation diversity modulationsymbols using an interleave pattern according to channel quality ofsubcarriers; an IQ combination section that combines the deinterleavedIch components and Qch components; and a demapping section that obtainsreceived data by demapping symbols after the combination.
 11. (canceled)12. The multicarrier reception apparatus according to claim 10, furthercomprising: a propagation path state estimation section that obtainschannel quality of subcarriers; and a transmission section thattransmits information indicating the channel quality of said subcarriersto the multicarrier transmission apparatus that transmits a signal onwhich said modulation diversity modulation symbols are superimposed,wherein a plurality of adjacent subcarriers are grouped and one piece ofchannel quality information per group out of the channel qualityinformation of said subcarriers is transmitted to said multicarriertransmission apparatus.
 13. The multicarrier reception apparatusaccording to claim 10, further comprising: a propagation path stateestimation section that obtains channel quality of subcarriers; and atransmission section that transmits information indicating the channelquality of said subcarriers to the multicarrier transmission apparatusthat transmits a signal on which said modulation diversity modulationsymbols are superimposed, wherein said channel quality information istransmitted to said multicarrier transmission apparatus at shorter timeintervals as a Doppler frequency increases.
 14. The multicarrierreception apparatus according to claim 10, further comprising: apropagation path state estimation section that obtains channel qualityof subcarriers; and a transmission section that transmits informationindicating the channel quality of said subcarriers to the multicarriertransmission apparatus that transmits a signal on which said modulationdiversity modulation symbols are superimposed, wherein when the Dopplerfrequency equals to or exceeds a predetermined value, transmission ofinformation indicating the channel quality of said subcarriers to saidmulticarrier transmission apparatus is stopped.
 15. The multicarrierreception apparatus according to claim 10, further comprising: apropagation path state estimation section that obtains channel qualityof subcarriers; and a transmission section that transmits informationindicating the channel quality of said subcarriers to the multicarriertransmission apparatus that transmits a signal on which said modulationdiversity modulation symbols are superimposed, wherein the channelquality of said subcarriers is classified according to the degree ofchannel quality and information indicating a class of subcarriers istransmitted to said multicarrier transmission apparatus as informationindicating the channel quality of said subcarriers.
 16. A multicarriercommunication method comprising: a step of detecting channel quality ofsubcarriers; and a modulation diversity modulation step of carrying outmodulation diversity modulation while adaptively changing an interleavepattern of Ich components and/or Qch components according to channelquality of subcarriers.